The present invention relates to semiconductor devices generally, and more specifically to packages and packaging methods for flip chip devices.
Flip chip technology provides a method for connecting an integrated circuit (IC) device to a substrate within a package. In the flip chip method, a plurality of electrical terminals are formed on an active face of the IC device. A respective solder bump is formed on each of the electrical terminals. The substrate has a plurality of terminal pads corresponding to the terminals on the IC device. The IC device is xe2x80x9cflipped,xe2x80x9d so that the terminals of the device contact the pads of the substrate. Heat is applied to reflow the solder bumps, forming electrical and mechanical connections between the substrate and the active face of the IC device.
The flip chip package is very compact, and is also referred to a chip-scale package. The flip chip device poses design challenges, because a thermal mismatch between the IC device and the substrate may cause a delamination failure. One method of reducing this problem is to place a heat spreader on the back (non-active) side of the IC device.
In U.S. Pat. No. 5,289,337 to Aghazadeh et al., FIG. 6 shows a heat spreader 26xe2x80x2 for shunting heat to the substrate 3. The heatspreader plate is held in position by an attachment ring 24xe2x80x2. The heatspreader plate 26xe2x80x2 contacts the substrate 3 through a layer of thermal grease 7. The entire package is hermetically sealed in a ceramic package having a plurality of leads. The package is installed in a printed circuit board (PCB), using the package leads. U.S. Pat. No. 5,289,337 is incorporated by reference herein in its entirety.
New thermal control configurations are desired for flip chip technology.
The present invention is a flip chip device having a heatspreader, wherein the heatspreader has a face, to which an inactive surface of the device is connected, and a plurality of legs which are connected to a substrate.
According to one aspect of the invention, a circuit board assembly, includes a substrate having a plurality of terminal pads. An IC device has a first and a second face. The first face of the device has a plurality of electrical interconnections to the terminal pads in the substrate. A heatspreader plate has a plurality of legs. The second face of the IC device is connected to the heatspreader plate by a first thermal interface material. Each of the plurality of legs is connected to the substrate by a second thermal interface material.
According to a second aspect of the invention, a method is provided for connecting a heatspreader to an IC device that is connected to a substrate in a flip-chip configuration. A first thermal interface material is used to connect a heatspreader plate to a non-active side of the IC device. The heatspreader plate has a plurality of legs. A second thermal interface material is used to connect each of the plurality of legs to the substrate.